1. Field of the Invention
The present invention refers to a connection system for connecting a cannula with a rounded cannula end and a chamber containing a flexible substance and two apertures, the flexible substance connecting both apertures via a channel, wherein the rounded cannula end is made of an inorganic material.
2. Description of the Related Art
Various connection systems between a catheter and a body are known in medical engineering. Patent specification WO 89/06987 describes a connection system between a port system implantable inside the human body tissue and a catheter. A port chamber is arranged in a human or animal body to which a catheter remaining inside the body and an external catheter, pushed from the outside into the port chamber, can be attached. The inside of the port chamber contains a silicon membrane which can be punctured by the external catheter. A cannula is attached to the external catheter to avoid damaging the membrane during puncturing, withthe cannula end puncturing the silicon membrane containing a spherical end. Such a system is sold under the PERCUSEAL.RTM. trademark. The disadvantage of this system is that the spherical end molded on the cannula is made of plastic. The plastic surface contains brows, is extremely rough and damages the silicon membrane when the cannula is inserted into the port chamber. A damaged silicon membrane can no longer satisfactorily fulfill its function of preventing foreign bodies from entering the body.
Furthermore, connection systems between a cannula carrier for subcutaneous or intravenous steel or Teflon cannulas and a catheter are known. In many cases the steel or Teflon cannula supported by a carrier attached to the skin is releasably connected to a puncturing tool which assists in pushingthe canula under the skin or into a vien. After correctly positioning the cannula, the puncturing tool is removed and an infusion catheter with a cannula support is coupled in its place. For the coupling, a pointed coupling cannula attached to the infusion catheter is used which is pushed into a respective receiving element in the cannula carrier. The insertion of the pointed coupling cannula is often problematic as an incorrect insertion angle can cause the tip to penetrate the side wall instead of running inside the guided channel. The infusion catheter also has to be secured to the cannula carrier with a fixing device to prevent detachment of the coupling cannula from the cannula carrier. Such a coupling mechanism is, for instance, described in patent specification WO 94/20160.
Connection systems between drug ampoules and an infusion catheter are also known. In most cases, the infusion catheter contains a female Luer at the end facing the ampoule with the ampoule containing a male Luer. A connection is formed by pushing the female Luer over the male Luer. The disadvantage of this system is that the connection between the male and female Luer is highly tolerance-dependent and that already slight angular deviations can cause a leak.